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Harvard Forest REU Symposium Abstract 2019

  • Title: Seedlings and energy equivalence: using CO2 and light curves to find productivity
  • Author: Alonwyn Clauser (Smith College)
  • Abstract:

    The global carbon cycle is the movement of carbon between the atmosphere, oceans, land. Human carbon emissions continues to increase the concentration of CO2 in our atmosphere causing unpredicted repercussions. Global models used to predict these changes to our ecosystems are not yet complete. Forest ecosystems are the least understood and seedlings are generally discounted in carbon models because of their high mortality rate, however seedlings’ metabolism and biomass contribute to ecosystem carbon fluxing by photosynthesizing and respiring. The energy equivalence theory states that population energy flux is independent of body mass; to test this theory I asked: How do dominant seedling species differ in their photosynthetic capacity? How do seedlings differ compared to older trees? I measured the photosynthetic capacity of seedlings by collecting CO2 and light curves using the LI-COR 6400XT. These curves were taken at Harvard Forest (Petersham, MA) with four species: red maple (Acer rubrum), red oak (Quercus rubra), white pine (Pinus strobus), and eastern hemlock (Tsuga canadensis). We also harvested tissue samples of the individuals for future analysis of carbon and nitrogen content, as well as water use efficiency. I expect there will be significant differences in the photosynthetic capacities of seedlings and mature trees. With my results, I can inform models to include these changing processes and allow for better and more accurate models to be made. These models would be used to help find the global carbon budget and predict the effects of climate change on our ecosystems.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions; Forest-Atmosphere Exchange